Xerochemical development of electrostatic images



United States Patent 3,392,018 XEROCHEMICAL DEVELOPNIENT OF ELECTROSTATIC IMAGES Kenneth A. Metcalfe, Fulham Park, South Australia, William A. Gold, North Adelaide, South Australia, and Frank C. Gillespie, Findon West, South Australia, Australia, assignors to The Commonwealth of Australia, The Secretary Department of Supply, Melbourne, Victoria, Australia No Drawing. Filed Apr. 11, 1963, Ser. No. 272,207 Claims priority, application Australia, Apr. 11, 1962, 16,475/ 62 19 Claims. (Cl. 96-1) This invention relates to a method of xerochemical development of electrostatic images.

Development of electrostatic images has in the past been carried out by applying to the image a developer which renders the image visible, the developer depositing according to the latent electrostatic image existing on the surface.

The methods of producing an electrostatic image on a surface are well known but generally comprise the use of a photoconductor medium embedded in an insulating base, the photoconductor medium being charged to give an overall potential on the surface and being then bled away image-wise by projecting a light image on to the surface, this electrostatic image being then capable of development by means of a toner powder or a liquid developer in accordance with the field existing at different parts of the image.

The developers applied to such an image must be of such a nature that they are self-fixing after application or they may be fixed by fusion or other means as is already well known in the art.

It is known to be advantageous to develop electrostatic images which do not require special or subsequent fixing and it is the object of this invention to provide an improved form of development of electrostatic images which will simplify the procedure generally and will give good and effective fixing of the image in a ready manner.

This is achieved according to the invention by combining both xerographic and chemical effects so that a developer is deposited xerographically but the image is produced chemically.

The method of developing electrostatic images thus comprises producing an electrostatic latent image on a base containing a photoconductor with or without a further catalyzing agent, developing the said electrostatic latent image with a developer comprising a photochemical substance capable of being catalyzed by the base, and subsequently rendering the image visible and fixed by subjecting the deposited developer to electromagnetic waves.

We have found for instance, that substances such as chloro-auric-acid or silver nitrate or copper sulphate or ferric chloride or lead oxide or bromo-platinic acid may be used as developers for zinc oxide and other photoconductive surfaces, the action being that the substances mentioned are deposited electrostatically on to a xerographic image and immediately after the image has been produced, and preferably while the deposited image is still wet, in the case of using a liquid developer, the image is subjected to electro-magnetic waves, preferably light, with the result that a chemical action takes place on the developer medium due to the catalyzing elfect of the photoconductor or other medium which results in a visible image being produced.

It has been found that such an image is adequately fixed to the surface due to the chemical reaction which has taken place, and therefore it is unnecessary to deposit with the developers any special fixing medium or any control substances, although the latter could be used it required, the deposition resulting in an image which is not in a visible or fixed condition until the chemical action takes place in the developer.

While it is envisaged that a convenient method of operating is to use a photo-conductor medium such as zinc oxide as the catalyst or chemical reagent, it will be obvious that it is possible to incorporate in the base with the photoconductor or the like a substance which itself could form the catalyst or chemical reagent for the developer, the same principle still applying in that a xerographic or electrostatic image is first produced which is then developed by xerographic methods and the image so produced is then subjected to conditions where a chemical reaction takes place in the developer to give a final visible and fixed image. Such a substance could be metallic zinc, platinum black or tin chloride.

The following examples serve to illustrate how the invention can be carried into effect:

Example 1 In the first example of the invention there is first pre pared a sheet of paper, wood, plastic or metal which is coated with a photo-conductive electro-photographic material such as a dispersion of zinc oxide in resin according to the following composition:

These materials are milled together in a single roll mill for one hour to produce a finely dispersed paint which is then applied after the required amount of dilution with further toluene appropriate to the coating method. For example the coating may be applied by roller, by brush, spray, electrostatic methods, knife or doctor blade to the required backing, to give a thickness which may vary from 0.1 micron to microns provided that the thickness is uniform to 10 percent accuracy on the particular sheet. The sheet is then cured at F. for 8 hours to produce uniform electrical properties. This sheet is then charged by electrostatic charging devices to produce a uniform surface charge and subsequently exposed to an optical or X-ray image to produce a latent electrostatic image. The latent electrostatic image is developed thereafter by subjecting it to a developer made in the following way:

Solution A.-A solution of the following proportions:

Solution B.-Solution A is dispersed in cyclohexane according to the following proportions:

Grams Solution A 10 Cyclohexane 100 Dispersion is effected by stirring the two together with a motor operated mixer or ultrasonic mixer to produce a colloidal dispersion.

The solution B or liquid developer is used to develop the latent electrostatic image by immersion or by roller application, the result being obtained by electrophoretic deposition. The resultant solid image is comprised of chloro-auric acid which is then exposed to light for example to the light emitted from a watt lamp at a distance of 12 inches for a period of one minute to darken the deposit by reducing it to gold, but in any case any exposure to light thereafter serves to darken the image or intensify it without impairment.

3 Example 2 In another embodiment of the invention, the electrophotographic coating of Example 1 is used but the developer comprises for Solution A the following:

Grams Cupric sulphate Dioxane 100 Solution B is made by dispersing Solution A to form a percent dispersion in Shell Solvent X55. Finally an image is produced which comprises the metal copper.

Example 3 In another embodiment of the invention the electrophotographic coating of Example 1 is replaced by vacuum evaporated selenium of the vitreous variety and the developer of Example 1 or 2 may be used.

Example 4 In another example of our invention, zinc oxide is replaced by the photoconductive form of bismuth trioxide in the formulation of the coating material and the developers of Example 1 or 2 may be used or alternatively the following developer may be used:

Solution A: Grams Bromo-platinic acid 3 Ethyl alcohol 100 Solution B is made by dispersing Solution A to form a five percent dispersion in Freon 113 or perchloroethylene by volume. The image comprises metallic platinum.

Example 5 In another example of our invention, the photoconductor zinc oxide is replaced by lead oxide, lead iodine,

cadmium sulphide or titanium dioxide and the developers are prepared as follows:

Solution A: Grams Silver nitrate 5 Dioxane 100 Solution B is made by dispersing Solution A to form a five percent dispersion in a solution of carbon tetrachloride in X4 solvent in the proportions 10 percent by volume. The final image comprises metallic silver.

Example 6 In another example of our invention, the photoconductor is zinc oxide, and the developer is prepared as follows:

Developer paste:

Silver nitrate grams Long oil alkyd resin, such as that sold by the Polymer Corporation under the trademark Rhodene PC 70 grams 3 A hydrocarbon solvent such as that sold by the Shell Company under the trademark Shellite cc 100 Example 7 In another example of our invention, the developer paste of Example 6 is modified by adding 10 grams of zinc oxide powder to the ingredients of the paste prior to milling. The developer paste is then dispersed in Shellite in the proportion 1 part of paste to 100 parts of Shellite and this dispersion is used to develop an electrostatic image. The image deposit comprises silver nitrate and zinc oxide and resin which after removal from the dark room and exposure to strong light is converted to a dark colored image.

What we claim is:

1. The method of developing electrostatic images which comprises producing an electrostatic latent image on a base containing a photoconductor, developing the said electrostatic latent image with a developer comprising an electrical insulating carrier liquid and photochemical substance dispersed therein immiscible with the carrier liquid and of a polarity in the carrier liquid to be attracted to the latent electrostatic image and capable of being catalyzed by a substance in the base when activated by electmomagnetic waves, and subsequently rendering the image visible and fixed by subjecting the deposited developer to electromagnetic waves.

2. The method of developing electrostatic images which comprises producing an electrostatic latent image on a base containing a photoconductor, developing the said electrostatic latent image with a developer comprising an electrical insulating carrier liquid and a photochemical substance dispersed therein immiscible with the carrier liquid and of a polarity in the carrier liquid to be attracted to the latent electrostatic image and capable of being catalyzed by the photoconductor in the base when activated by electromagnetic waves, and subsequently rendering the image visible and fixed by subjecting the deposited developer to electromagnetic waves.

3. The method of developing electrostatic images which comprises producing an electrostatic latent image on a base containing a photoconductor and a catalyzing agent, developer comprising an electrical insulating carrier liquid and a photochemical substance dispersed therein immiscible with the carrier liquid and of a polarity in the carrier liquid to be attracted to the latent electrostatic image and capable of being catalyzed by the catalyzing agent in the base when activated by electromagnetic waves, capable of being catalyzed by the said catalysing agent, and subsequently rendering the image visible and fixed by subjecting the deposited developer to electromagnetic waves.

4. The method of developing electrostatic images which comprises producing an electrostatic latent image on a base containing a photoconductor, developing the said electrostatic latent image with a developer comprising an electrical insulating carrier liquid and a photochemical substance dispersed therein immiscible with the carrier liquid and of a polarity in the carrier liquid to be attracted to the latent electrostatic image and capable of being catalyzed by a substance in the base when activated by electromagnetic waves, said photochemical substance being selected from the group consisting of chloro-auric-acid, silver nitrate, copper sulphate, ferric chloride, lead oxide and bromo-platinic acid, and subsequently rendering the image visible and fixed by subjecting the deposited developer to electromagnetic waves.

5. The method of developing electrostatic images which comprises producing an electrostatic latent image on a base containing a photoconductor, developing the said electrostatic latent image with a developer comprising an electrical insulating carrier liquid and photochemical substance dispersed therein immiscible with the carrier liquid and of a polarity in the carrier liquid to be attracted to the latent electrostatic image and capable of being catalyzed by the photoconductor in the base when activated by electromagnetic waves, said photochemical substance being selected from the group consisting of chloroauric-acid, silver nitrate, copper sulphate, ferric chloride, lead oxide and bromo-platinic acid, and subsequently rendering the image visible and fixed by subjecting the deposited developer to electromagnetic waves.

6. The method of developing electrostatic images which comprises producing an electrostatic latent image on a base containing a photoconductor and a catalyzing agent, developing the said electrostatic latent image with a developer comprising an electrical insulating carrier liquid and a photochemical substance dispersed therein immiscible with the carrier liquid and of a polarity in the carrier liquid to be attracted to the latent electrostatic image and capable of being catalyzed by the catalyzing agent in the base when activated by electromagnetic waves, said photochemical substance being selected from the group consisting of chloro-auric-acid, silver nitrate, copper sulphate, ferric chloride, lead oxide and bromo-platinic acid, and subsequently rendering the image visible and fixed by subjecting the deposited developer to electromagnetic Waves.

7. The method of developing electrostatic images which comprises producing an electrostatic latent image on a base containing a photoconductor selected from the group consisting of zinc oxide, selenium, lead oxide, and bismuth trioxide, developing the said electrostatic latent image with a developer comprising an electrical insulating carrier liquid and a photochemical substance dispersed therein immiscible with the carrier liquid and of a polarity in the carrier liquid to be attracted to the latent electrostatic image and capable of being catalyzed by the photoconductor in the base when activated by electromagnetic waves, and subsequently rendering the image visible and fixed by subjecting the deposited developer to electromagnetic waves.

8. The method according to claim 7 wherein the electromagnetic waves are light.

9. The method according to claim 7 wherein the electromagnetic waves are heat.

10. The method according to claim 7 wherein the electromagnetic waves are X-rays.

11. The method of developing electrostatic images which comprises producing an electrostatic latent image on a base containing a photoconductor selected from the group consisting of zinc oxide, selenium, lead oxide, and bismuth trioxide, developing the said electrostatic latent image with a developer comprising an electrical insulating carrier liquid and a photochemical substance dispersed therein immiscible with the carrier liquid and of a polarity in the carrier liquid to be attracted to the latent electrostatic image and capable of being catalyzed by the photoconductor in the base when activated by electromagnetic waves, said photochemical substance being selected from the group consisting of chloro-auric-acid, silver nitrate, copper sulphate, ferric chloride, lead oxide and bromoplatinic acid, and subsequently rendering the image visible and fixed by subjecting the deposited developer to electromagnetic Waves.

12. The method according to claim 11 wherein the electromagnetic waves are light.

13. The method according to claim 11 wherein the electromagnetic waves are heat.

14. The method according to claim 11 wherein the electromagnetic waves are X-rays.

15. The method of developing electrostatic images which comprises producing an electrostatic latent image on a base containing a photoconductor and a catalyzing agent selected from the group consisting of metallic zinc, platinum black and tin chloride, developing the said electrostatic latent image with a developer comprising an electrical insulating carrier liquid and a photochemical substance dispersed therein immiscible with the carrier liquid and a polarity in the carrier liquid to be attracted to the latent electrostatic image and capable of being catalyzed by the catalyzing agent in the base when activated by electromagnetic waves, and subsequently rendering the image visible and fixed by subjecting the deposited developer to electromagnetic waves.

16. The method of developing electrostatic images which comprises producing an electrostatic latent image on a base conaining a photoconductor and a catalyzing agent selected from the group consisting of metallic zinc, platinum black and tin chloride, developing the said electrostatic latent image with a developer comprising an electrical insulating carrier liquid and a photochemical substance dispersed therein immiscible with the carrier liquid and of a polarity in the carrier liquid to be attracted to the latent electrostatic image and capable of being catalyzed by the catalyzing agent in the base when activated by electromagnetic waves, said photochemical substance being selected from the group consisting of chloroauric-acid, silver nitrate, copper sulphate, lead oxide, and 'bromo-platinic acid, and subsequently rendering the image visible and fixed by subjecting the deposited developer to electromagnetic waves.

17. The method according to claim 16 wherein the electromagnetic waves are light.

18. The method according to claim 16 wherein the electromagnetic waves are heat.

19. The method according to claim 16 wherein the electromagnetic waves are X-rays.

References Cited UNITED STATES PATENTS 3,072,541 1/1963 Shely et al. 961 3,033,117 3/1963 Schmiedel et al. 96-1 3,142,562 7/1964 Blake 961 3,152,903 10/1964 Shepard et al. 9664 3,231,374 1/1966 Sciarnbi 96-1 3,052,541 9/1962 Levinos 96-27 3,068,115 12/1962 Gundlach 96-1 X OTHER REFERENCES Metcalfe et al.: Xerography, Journal of Oil and Color Chemists Association, vol. 39, No. 11, pp. 851-853.

NORMAN G. TORCHIN, Primary Examiner.

I. TRAVIS BROWN, Examiner.

C. E. VANHORN, Assistant Examiner. 

1. THE METHOD OF DEVELOPING ELECTROSTATIC IMAGES WHICH COMPRISES PRODUCING AN ELECTROSTATIC LATENT IMAGE ON A BASE CONTAINING A PHOTOCONDUCTOR, DEVELOPING THE SAID ELECTROSTATIC LATENT IMAGE WITH A DEVELOPER COMPRISING AN ELECTRICAL INSULATING CARRIER LIQUID AND PHOTOCHEMICAL SUBSTANCE DISPERSED THEREIN IMMISCIBLE WITH THE CARRIER LIQUID AND OF A POLARITY IN THE CARRIER LIQUID TO BE ATTRACTED TO THE LATENT ELECTROSTATIC IMAGE AND CAPABLE OF BEING CATALYZED BY A SUBSTANCE IN THE BASE WHEN ACTIVATED BY ELECTMOMAGNETIC WAVES, AND SUBSEQUENTLY RENDERING THE IMAGE VISIBLE AND FIXED BY SUBJECTING THE DEPOSITED DEVELOPER TO ELECTROMAGNETIC WAVES. 